1. Field of the Invention
This invention relates to apparatus for and methods of directing fibers and more particularly to directing a gas entrained stream of fibers while it is in flight between a fiberizing unit and a collection surface.
2. Description of the Prior Art
In the process of forming mats of inorganic fibrous material it has been known to fiberize the material in a fluid stream such as a hot gas blast, a stream jet, or a stream of air which entrains the fiber in a stream of limited transverse extent, frequently of generally circular cross-section, which has been termed a "veil." Fiber in the veil has been directed on a moving collector screen which can have a suction box at a few inches of vacuum on its opposite face to enhance the fiber desposition. Where collector screen velocity through the collection region is low enough, the fiber veil is such as to permit fiber dispersion over the collection region, and/or a sufficient vacuum is drawn, fibers will be distributed over the collector by the gas flow to the paths of lower flow resistance presented by the thinner regions of the mat of fibers being developed on the collector screen. At higher speeds of production and/or with more concentrated fiber veils the fibers tended to build to a great extent on a localized region of the collector screen; for example, with the veil directed to the screen center viewed in the direction of travel there was a tendency to concentrate fiber in the center of the mat being formed with a thinner or lighter weight deposition of fiber toward the longitudinal edges when so viewed.
In order to enhance fiber distribution, it was proposed in Snow et al. U.S. Pat. No. 2,863,493 of Dec. 9, 1958 entitled "Method and Apparatus of Forming and Processing Fibers" that nozzles be located on opposite sides of the region through which a veil of fibers is passed from a fiberizer to a collector screen and that a blast of air be applied alternately from the opposed nozzles to shift the veil in the collection chamber transverse of the path of advance of the collection screen. The alternate air blasts were controlled by a rotary valve mechanism having a barrel which was driven in rotation by a worm and gear from a motor to couple a source of air under pressure alternately to conduits extending to the opposed nozzles.
Another fiber manipulating arrangement is disclosed in Stalego et al. U.S. Pat. No. 2,897,874 of Aug. 4, 1959 entitled "Method and Apparatus of Forming, Processing and Assembling Fibers" wherein the generally circular cross-sectional veil of fibers from a fiberizer is formed into a loose planar web during its flight toward a collecting screen and is lapped back and forth across the width of the screen in the direction of advance of the screen by arrays of nozzles supplied with compressed air. Opposed arrays of nozzles are provided on each side of the flattened web or veil and transverse thereof over its full width so that a two-way motor driven valve control can shift the blast from one array to the other alternately.
Berthon et al. U.S. Pat. No. 3,020,585 of Feb. 13, 1962 for "Process and Apparatus for the Manufacture of Fiber Linings or Mats" employs continuous jets of air or gas to flatten a vortex or veil of fibers to a sheet form while in flight to a collecting screen surface. In some embodiments disclosed by Berthon et al. one or more nozzles are moved along regular paths in a cyclic manner by mechanical drives to change the attitude of their jet or jets with respect to the veil of fibers.
None of the methods or apparatus of the above-mentioned discloses lent themselves to variation of the control of the fiber direction without modification of the mechanical elements.
An object of the present invention is to enhance the control of the direction of a stream of fibers entrained in a fluid stream.
Another object is to enable adjustment of the control of the direction of a stream of fibers.
A further object is to control adjustably the frequency of gaseous jet pulsations applied in the directing of a stream of fibers in flight.
A fourth object is to control adjustably the interval a gaseous jet is imposed on a stream of fibers in flight to control their direction. In this regard independence between interval adjustment and frequency adjustment is desirable to control weight distribution of fibers on a collector surface.
A fifth object is to actuate valving electrically and develop control signals electrically to enhance flexibility of control both in set up of a system and during operation of the system.